Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Analysis of Variance”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,675 records · Page 93Linked to original sources
PubMed2006

Feasibility of soil dust source apportionment by the pyrolysis-gas chromatography/mass spectrometry method.

This study tested the feasibility of using pyrolysis (Py)-gas chromatography (GC)/mass spectrometry (MS) to obtain organic chemical species data suitable for source apportionment modeling of soil-derived coarse particulate matter (PM10) dust on ambient filters. A laboratory resuspension apparatus was used with known soils to generate simulated receptor filter samples loaded with approximately 0.4 mg of PM10 dust, which is within the range of mass loading on ambient filters. Py-GC/MS at 740 degrees C generated five times more resolvable compounds than were obtained with thermal desorption GC/MS at 315 degrees C. The identified compounds were consistent with literature from Py experiments using larger samples of bulk soils. A subset of 91 organic species out of the 178 identified Py products was used as input to CMB8 software in a demonstration of source apportionment using laboratory-generated mixtures simulating ambient filter samples. The 178 quantified organic species obtained by Py of soil samples is an improvement compared with the 38 organic species obtained by thermal desorption of soils and the four functionally defined organic fractions reported by thermal/ optical reflectance. Significant differences in the concentration of specific species were seen between samples from different sites, both geographically distant and close, using analysis of variance and cluster analysis. This feasibility study showed that Py-GC/MS can generate useful source profile data for receptor modeling and justifies continued method development.

Cluster Analysis↗
PubMed2002

Health-related quality-of-life assessment of prenatal diagnosis: chorionic villi sampling and amniocentesis.

This study assesses the health-related quality-of-life (HRQL) effects of chorionic villi sampling (CVS) and genetic amniocentesis (GA), including both process and outcomes of prenatal diagnosis. The HRQL of 126 women participating in a randomized controlled clinical trial of CVS versus GA in Toronto and Hamilton, Ontario, was assessed in four interviews at weeks 8, 13, 18, and 22 of pregnancy. Statistical analyses included analysis of variance, repeated measures analysis of covariance, chi-square, Fisher's exact test, Student's t-tests, and paired t-tests. Utility scores for patients undergoing CVS exceeded those for GA patients at week 18 (p = 0.04). Utility scores for hypothetical health states did not differ significantly by trial arm. CVS results in slightly improved HRQL during prenatal diagnosis. This advantage needs to be weighed against the high disutility patients attach to infrequent outcomes associated with pregnancy losses, equivocal diagnoses, and diagnostic inaccuracy.

Adult↗
PubMed2001

Clinical impact of interlaboratory variation in international normalized ratio determinations.

Variation among laboratories and point-of-care (POC) devices in International Normalized Ratio (INR) determinations for individual patients in the same community was studied. For each patient, blood samples obtained from a single venipuncture followed by a finger stick were tested at three laboratories and with two POC devices. A nonparametric analysis of variance and regression analysis were used to compare INRs across sources. The potential clinical impact of differences between pairs of INR readings (i.e., whether a difference was likely to result in a change in therapy) was evaluated. Complete data were obtained and analyzed for 41 patients. Of the five sources of INRs, results from two laboratories and one POC device were significantly similar. Results from one laboratory and one POC device were significantly different from the other results. Variation between INR readings from two different sources might have resulted in a change in therapy 10-30% of the time. Variations occurred in INR readings among three laboratories and two POC devices and could have led to a substantial number of inappropriate changes in therapy.

Anticoagulants↗
PubMed2000

Relationships among age-associated strength changes and physical activity level, limb dominance, and muscle group in women.

This study investigated the magnitude and rate of age-associated strength reductions in Australian independent urban-dwelling women and the relationship to muscle groups, limb dominance, and physical activity level. Independent urban-dwelling women aged 20 to 89 years (N = 217) performed maximal voluntary contractions with the dominant and nondominant knee extensors, plantar flexors, and handgrip. Anthropometric measurements were made and questionnaire responses used to obtain current physical activity levels. Trend analysis within analysis of variance and regression analysis on strength was performed. Limb muscle strength was found to be associated with increased age, muscle group, limb dominance, and activity. Self-reported physical activity levels declined with age but women who were more physically active for their age group were stronger in all muscle groups and had more lean body mass and lean thigh and leg cross-sectional area than relatively inactive women. Slopes of the linear reductions of maximal voluntary strength of the knee extensors, plantar flexors, and handgrip with age were significantly different (p < .05) at 9.3%, 7.4%, and 6.2% per decade, respectively. The limb muscle strength of healthy Australian independent and urban-dwelling women aged 20 to 89 years was found to be associated with age and three aspects of disuse: muscle group, relative levels of physical activity, and limb dominance.

Adult↗
PubMed1994

Brinley plots, explained variance, and the analysis of age differences in response latencies.

Critics of Brinley plot analyses (e.g., Fisk, Fisher, & Rogers, 1992; Perfect, 1994) claim: (a) that lack of overlap between latencies on different tasks inflates r2 values; (b) that Brinley plots mask task-specific age differences; and (c) that measurement error in young adults' latencies precludes the use of regression techniques with Brinley plot data. We dispute these claims. We show that lack of overlap does not inflate r2 and that the possible presence of task-specific effects in Brinley plot data may be evaluated using standard regression techniques. These techniques are illustrated using data from the Fisk and Rogers (1991) study of visual and memory search. Analysis of their data reveals significant differences between the lexical and nonlexical domains, but not between types of search. Finally, the effect of measurement error on Brinley plot analyses is shown to be small and, if taken into account, leads to increased support for general cognitive slowing.

Adolescent↗
PubMed2002

Guidelines for the design and statistical analysis of experiments using laboratory animals.

For ethical and economic reasons, it is important to design animal experiments well, to analyze the data correctly, and to use the minimum number of animals necessary to achieve the scientific objectives---but not so few as to miss biologically important effects or require unnecessary repetition of experiments. Investigators are urged to consult a statistician at the design stage and are reminded that no experiment should ever be started without a clear idea of how the resulting data are to be analyzed. These guidelines are provided to help biomedical research workers perform their experiments efficiently and analyze their results so that they can extract all useful information from the resulting data. Among the topics discussed are the varying purposes of experiments (e.g., exploratory vs. confirmatory); the experimental unit; the necessity of recording full experimental details (e.g., species, sex, age, microbiological status, strain and source of animals, and husbandry conditions); assigning experimental units to treatments using randomization; other aspects of the experiment (e.g., timing of measurements); using formal experimental designs (e.g., completely randomized and randomized block); estimating the size of the experiment using power and sample size calculations; screening raw data for obvious errors; using the t-test or analysis of variance for parametric analysis; and effective design of graphical data.

Animal Welfare↗
PubMed1988

Changes in innominate tilt after manipulation of the sacroiliac joint in patients with low back pain. An experimental study.

The purposes of this study were to 1) propose a method to detect sacroiliac joint dysfunction (SIJD), 2) test the interrater reliability of the method on a group of patients with low back pain (LBP), and 3) document changes in innominate tilt after manipulation of the sacroiliac joint. Criteria for SIJD were established by the authors. Twenty-six patients with unilateral LBP were examined independently for presence of SIJD by two examiners. Interrater agreement for presence or absence of SIJD was found to be excellent (Cohen's Kappa = .88). Twenty of the patients who met the criteria for SIJD were randomly assigned to an Experimental Group (n = 10) or a Control Group (n = 10). The left and right innominate bones of these 20 patients were measured for tilt before and after the intervention period. The sacroiliac joint of the patients in the Experimental Group was manipulated during the intervention period, whereas the patients in the Control Group received no treatment. Data were analyzed using a mixed three-factor analysis of variance. The data analysis revealed that the manipulation procedure resulted not only in an altered innominate tilt of the same side but also in an equal and opposite tilt of the opposite side (F = 67.07; df = 1.18; p less than .05). The results indicate that SIJD can be identified reliably in patients with LBP and that a manipulative procedure purported to be specific to the sacroiliac joint changes innominate tilt bilaterally and in opposite directions.

Adolescent↗
PubMed2001

Direct current auditory evoked potentials during wakefulness, anesthesia, and emergence from anesthesia.

Direct current auditory evoked potentials (DC-AEPs) are a sensitive indicator of depth of anesthesia in animals. However, they have never been investigated in humans. To assess the potential usefulness of DC-AEPs as an indicator of anesthesia in humans, we performed an explorative study in which DC-AEPs were recorded during propofol and methohexital anesthesia in humans. DC-AEPs were recorded via 22 scalp electrodes in 19 volunteers randomly assigned to receive either propofol or methohexital. DC-AEPs were evoked by binaurally presented 2-s, 60-dB, 800-Hz tones; measurements were taken during awake baseline, anesthesia, and emergence. Statistical analysis included analysis of variance and discriminant analysis of data acquired during these three conditions. About 500 ms after stimulus presentation, DC-AEPs could be observed. These potentials were present only during baseline and emergence-not during anesthesia. Statistically significant differences were found between baseline and anesthesia and between anesthesia and emergence. In conclusion, similar effects, as reported in animal studies of anesthetics on the DC-AEPs, could be observed in anesthetized humans. These results demonstrate that DC-AEPs are potentially useful in the assessment of cortical function during anesthesia and might qualify the method for monitoring anesthesia in humans.

Adult↗
PubMed1990

Survey results: identification of research interests and needs in SGNA.

The purpose of this study was to determine the interest level and needs of the Society of Gastroenterology Nurses and Associates (SGNA) to develop a research program for (SGNA), whose members care for patients with gastrointestinal (GI) problems. A questionnaire mailed to all members (3500) focused on their research interest and experience, and 358 questionnaires were returned (return rate 10%). Data were analyzed with descriptive statistics, analysis of variance, and content analysis. Educational levels were: 8% LPN, 32% RN, 16% AD, 31% BA/BS, 9% MA/MS. Sixty-seven percent were employed in GI endoscopy laboratories. Approximately 35% had some type of research experience. The mean level of interest in research, rated on a scale of 0 (none) to 10 (high), was 6.6 (+/- 2.3). There was a significant difference between education and interest levels (RN and AD mean = 6.2, MS and "other" mean = 7.6). Moderate interest was expressed for all aspects of research (data collection--highest; finding funding--lowest). Two commonly expressed needs were for information about current GI research and how to begin the research process. The most frequently cited clinical problems needing study were infection control, staffing, and intra-procedure medication use and monitoring. This study demonstrated an interest in research among GI nurses of varied educational backgrounds and experience. Nurses in practice have observed many areas of concern and recognize the value of research to contribute to the improvement of their practice.

Gastrointestinal Diseases↗
PubMed1994

Using chart reviews to assess residents' performances of components of physical examinations: a pilot study.

PURPOSE: To evaluate chart review as a method of assessing residents' performances of physical examinations in an ambulatory care setting. METHOD: In 1992, nurse authors at the Affiliated Hospitals at Canton of the Northeastern Ohio Universities College of Medicine assessed whether 22 internal medicine residents performed ten components of the physical examination by interviewing patient volunteers immediately after the patients' examinations. A total of 89 patient interviewees were included in the analysis; these patients were all new outpatients who had been scheduled for initial visits to obtain complete histories and physical examinations. Charts for the same patients were then retrospectively reviewed. The residents and faculty were blinded to both the chart reviews and the interviews. Statistical methods used were Pearson correlational analysis and variance-component analysis. RESULTS: The interviews and chart reviews showed 81% agreement in component performance. Completeness of the physical examination (whether measured by chart review or interview) did not correlate with other standard methods of resident evaluation, and completeness did not show a significant association with characteristics of the residents and patients. Two of the 22 residents assessed were identified as having completeness scores so low as to be unsatisfactory. CONCLUSION: That residents were identified as failing to perform examination components suggests that chart reviews, especially when independently verified by patient interviews, may be a useful evaluation tool for identifying inadequate performance of components of the physical examination and may identify the need for remediation.

Adult↗
PubMed2000

Relationship between arterial, mixed venous, and internal jugular carboxyhemoglobin concentrations at low, medium, and high concentrations in a piglet model of carbon monoxide toxicity.

OBJECTIVE: This study tested the hypothesis that mixed venous carboxyhemoglobin concentrations (V-COHb) and internal jugular carboxyhemoglobin concentrations (I-COHb) accurately predict arterial carboxyhemoglobin concentrations (A-COHb). In addition, this study tested the hypothesis that there is a high correlation at low (COHb, 0% to 10%), moderate (COHb, >10% to 40%), and high (COHb, >40%) concentrations between V-COHb, I-COHb, and A-COHb. DESIGN: The study was a prospective comparison of A-COHb, V-COHb, and I-COHb concentrations in piglets exposed to increasing concentrations of carbon monoxide over 6 hrs to achieve a concentration of > or =60% COHb. Carboxyhemoglobin measurements were evaluated by analysis of variance and correlation analysis. Agreement between V-COHb and A-COHb concentrations was examined by using a plot of arteriovenous differences against the mean of the two measurements. INTERVENTION: We simultaneously sampled arterial, mixed venous, and internal jugular blood every 30 mins over the 6-hr study period. RESULTS: Two hundred fifty arterial and mixed venous COHb concentrations were obtained, and 214 internal jugular COHb concentrations were obtained. One hundred additional arterial, mixed venous, internal jugular, and peripheral COHb concentrations were obtained. Correlation between samples at each concentration revealed r2 > = .94. CONCLUSION: Venous COHb concentrations predict arterial COHb concentrations with a high degree of accuracy and are correlated at low, moderate, and high concentrations of carbon monoxide exposure. Arterial or venous samples can be used to accurately measure COHb concentrations.

Animals↗
PubMedDate not supplied

Racial and socioeconomic differences in risk factors for cardiovascular disease among Southern rural women.

BACKGROUND: African American women living in the Southeast experience a higher mortality due to cardiovascular (CV) disease than their White counterparts. It is unclear if this vulnerability to CV disease is due to race, socioeconomic status, or health behaviors. OBJECTIVES: To examine the disparities in cardiovascular health between Southern rural, African American and White women to determine if a CV Risk-Index differed by race, education, or income levels and if differences persisted when controlling for body mass index (BMI). METHODS: Subjects were 1,110 women (27% African American, 73% White) residing in rural North Carolina. Data were collected by mailed questionnaire and analyzed using analysis of variance (ANOVA) and analysis of covariance (ANCOVA). RESULTS: African American women had significantly lower education and lower income than Whites, higher BMI, and a much greater prevalence of hypertension, angina, and diabetes. In a three-way ANOVA including race, income, and education, education and race were significant predictors of the CV Risk Index, but when adjusted for BMI race was no longer significant (p =.3039); the only significant predictors were BMI and educational level. DISCUSSION: Women with the least education had the highest CV Risk-Index, regardless of race. These findings suggest the need to focus risk reduction interventions on all Southern rural women with limited education, not only African American women. This supports the current literature that suggests race should be viewed as a risk marker rather than a risk factor.

Adult↗
PubMedDate not supplied

The menstrual cycle and platelet 5-HT uptake.

The association between the onset of depressive illness and the paramenstruum has been reported. In the present study, we looked at changes in platelet 5-HT uptake in six healthy, regularly menstruating subjects on days 1, 10, and 24 of three consecutive menstrual cycles to explore possible biochemical bases for mood changes associated with menstruation. Platelet 5-hydroxytryptamine (5-HT) uptake was determined by suspension of platelet pellets in 0.5-5 microM hydroxy [G-3H] tryptamine [( 3H]-5-HT) creatinine sulfate solution at 37 degrees C and measurement of radioactivity of [3H]-5-HT in the platelets using liquid scintillation counting. Mood changes were measured using the Moos Menstruation Distress Questionnaire and the Spielberger State Anxiety Scale. Analysis of variance and trend analysis revealed significant elevation of Km and Vmax on day 24 of the cycle, which was consistent across the three menstrual cycles studied. A significant linear rise of "negative affect" across each cycle peaking on day 1 was detected. "Water retention" and "behavioral change" also peaked on day 1. No significant correlation, however, was obtained between the mood scores and platelet 5-HT uptake. These findings are discussed.

Adult↗
PubMed2002

Characterization of the cerebral blood flow response to balloon deflation after temporary internal carotid artery test occlusion.

The authors tested the hypothesis that cerebral blood flow (CBF) would increase after acute and relatively brief internal carotid artery (ICA) test occlusion, and examined the relationship of the postdeflation CBF to the development of neurologic symptoms. In 16 patients undergoing ICA test occlusion with deliberate hypotension, the authors measured intracarotid 133Xe CBF at baseline, occlusion, and deflation. Four patients developed neurologic symptoms during occlusion. As positive controls, 11 other patients received intracarotid verapamil or papaverine before deflation as part of another protocol. Balloon occlusion was 23.1 +/- 10.5 minutes (mean +/- standard deviation) in duration. At 1.3 +/- 1.6 minutes after balloon deflation, there was a trend (12 +/- 31%) for CBF to increase (48 +/- 9 mL/100 g/min versus 53 +/- 17 mL/100 g/min, P =.15), and a 16 +/- 27% decrease in cerebrovascular resistance (CVR; 2.1 +/- 0.6 mm Hg/100 g/min/mL versus 1.7 +/- 0.6 mm Hg/100 g/min/mL, P =.03) compared with baseline values. By comparison, patients who received a intracarotid dilator demonstrated a 53 +/- 55% increase in CBF (48 +/- 10 mL/100/min versus 70 +/- 23 mL/100 g/min, P = .007) and a 33 +/- 31% decrease in CVR (2.2 +/- 0.6 mm Hg/100 g/min/mL versus 1.4 +/- 0.6 mm Hg/100 g/min/mL, P = .0007) compared with baseline. Analysis of variance and regression analysis showed no other relationships between postocclusion CBF and balloon occlusion duration, distal internal carotid occlusion ("stump") pressure, or the development of neurologic symptoms. Acute, temporary interruption of ICA blood flow resulted in minimal postocclusive changes in cerebrovascular hemodynamics, even in those patients who developed neurologic symptoms during the period of test occlusion.

Adult↗
PubMed2005

The influence of pregnancy on arterial compliance.

OBJECTIVE: To examine the effect of pregnancy and the interval between pregnancies on arterial compliance as measured by mean arterial pressure (MAP) and pulse pressure. METHODS: We conducted a 3-month chart review of deliveries at a tertiary care hospital (index pregnancies). Data collected included demographics, obstetric history, blood pressures, prepregnancy weight, weight gain, and neonatal outcome. If a subject's first delivery occurred at our institution, these records were reviewed in a similar fashion. Mean antepartum MAP and pulse pressure were calculated and compared for each trimester between index and first pregnancies. Statistical methods employed included repeated measures analysis of variance, repeated measures analysis of covariance, and correlation analysis. RESULTS: Two hundred eighty-five charts were reviewed. Forty-seven women had complete data covering both index and first pregnancy. Mean arterial pressure was significantly higher in all trimesters of first compared with index pregnancies (first pregnancy-first trimester 82.0 +/- 8.1 mm Hg, index pregnancy-first trimester 79.4 +/- 7.6 mm Hg, P = .032; first-second trimester 81.6 +/- 6.7 mm Hg, index-second trimester 78.7 +/- 6.6 mm Hg, P = .016; first-third trimester 83.9 +/- 6.9 mm Hg, index-third trimester 81.6 +/- 6.9 mm Hg, P = .047). Repeated measures analysis of covariance confirmed that pregnancy order contributed independently to differences in MAP. The interval between pregnancies was found to be inversely related to the difference in MAP from first to index pregnancies by trimester (r = -0.41, P = .004) and the change in MAP within pregnancy from first to third trimester (r = -0.31, P = .046). CONCLUSION: Mean arterial pressure is reduced in subsequent pregnancies compared with first pregnancies. This raises the possibility that pregnancy plays a role in modifying cardiovascular compliance. Consistent with this, the effect has temporal limitations in that the shorter the interval between pregnancies, the greater the reduction in MAP.

Adult↗
PubMed2003

ProDisc artificial total lumbar disc replacement: introduction and early results from the United States clinical trial.

STUDY DESIGN: Multicenter prospective randomized study of artificial disc replacement (ProDisc) versus circumferential fusion (standard of care) for one- and two-level degenerative disc disease. This is an interim analysis on patients seen at the Spine Institute Saint John's Health Center, Santa Monica, California. OBJECTIVES: To evaluate early pain and functional outcomes of patients treated with disc replacement or fusion and to assess the capacity of this intervertebral disc replacement for preserving motion in the lumbar spine. SUMMARY OF BACKGROUND DATA: Disc replacement is intended to reduce pain via removal of the diseased disc while restoring physiologic motion and height at the affected level. The long-term physiologic advantage of disc replacement to fusion is that preservation of motion may prevent additional degeneration at adjacent levels. METHODS: Patients meeting inclusion criteria were consented for study. Randomization was performed using a 2 to 1 ratio of disc replacement procedure to a fusion procedure. Patients rated their pain on the Visual Analogue Scale and completed the Oswestry Disability Index questionnaire. Radiographs were taken. Assessments were made before surgery and after surgery at 6 weeks, 3 months, 6 months, and 1 year (ongoing). Changes from preoperative pain, disability, or motion were separately evaluated as a function of treatment using repeated measures mixed design analysis of variance. RESULTS: This analysis includes data up to 6 months from the first 53 randomized patients. There were 35 patients who underwent disc replacements, and 18 patients had fusion procedures. Disc replacement patients had a significant reduction in pain and disability at earlier evaluations. By 6 months, the relative improvement on both the Visual Analogue Scale and Oswestry (both, P < 0.05) were similar for disc replacement and fusion patients. Greater motion was found at L4-L5 for disc replacement patients (P < 0.05) than fusion patients. A similar trend was noted at L5-S1 (P was not significant). CONCLUSIONS: Disc replacement patients reported significantly less pain (Visual Analogue Scale) and disability (Oswestry) in the early period following surgery compared to fusion patients. This difference disappeared by 6 months. When compared to fusion, the disc replacement allowed preservation of motion at L4-L5 with a similar trend at L5-S1.

Adult↗
PubMed2005

Comparison of axial and tangential topographic algorithms for contact lens fitting after LASIK.

PURPOSE: Computerized videokeratography (CVK) has become the standard method for measuring the corneal curvature after refractive surgery. However, few resources exist on the use of CVK data for postoperative contact lens fitting, and no recommendations exist on the selection of the best topographic algorithm relevant to gas-permeable (GP) lens fitting. This study assessed the optimal use of topographic data to fit spherical GP contact lenses on patients who have undergone laser in situ keratomileusis. METHODS: A retrospective analysis of CVK maps from eight post-LASIK eyes fitted with spherical GP lenses was performed in the Contact Lens Service of the Department of Ophthalmology at Case Western Reserve University and University Hospitals of Cleveland. Axial and tangential maps from the Dicon CT 200 (version 3.50) or Humphrey Atlas (version A8) topographer were analyzed. Averaged dioptric curvatures from different locations (inferior, superior, and temporal) at various distances (2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm, and 4.0 mm) from the vertex normal of each eye were compared with the base curves of the prescribed GP contact lenses. RESULTS: One-way analysis of variance, Pearson correlation analysis, and paired t tests showed that the best topographic predictors of a successful GP base curve were the average curvatures at the 4.0 mm distance on the axial maps (r=0.8078, P=0.05) and at the 2.0 mm distance on the tangential maps (r=0.9738, P=0.0002). The mean dioptric powers of the GP base curve, axial map 4.0 mm curvature, and tangential map 2.0 mm curvature were 41.50 diopters (D), 42.65 D, and 42.67 D, respectively. CONCLUSION: To simplify and guide GP fitting after LASIK, the average dioptric curvature 4.0 mm from the vertex normal on axial maps or 2.0 mm from the vertex normal on tangential maps are the best predictors of accurate GP base curve selection.

Algorithms↗
PubMed2006

Assessing cortical functional connectivity by partial directed coherence: simulations and application to real data.

The aim of this paper is to test a technique called partial directed coherence (PDC) and its modification (squared PDC; sPDC) for the estimation of human cortical connectivity by means of simulation study, in which both PDC and sPDC were studied by analysis of variance. The statistical analysis performed returned that both PDC and sPDC are able to estimate correctly the imposed connectivity patterns when data exhibit a signal-to-noise ratio of at least 3 and a length of at least 27 s of nonconsecutive recordings at 250 Hz of sampling rate, equivalent, more generally, to 6750 data samples.

Algorithms↗